An increasing depth of integration in planar light circuits (PLCs) means that waveguide crossings can be avoided to a lesser and lesser extent. By way of example, attenuator units are used to perform a channel-dependent attenuation of the levels of the signals of individual data channels of an array of waveguides. Different levels can be equalized by means of a channel-dependent attenuation. For metrological monitoring of the individual channels of the array, a small part of the optical power (usually between one and ten percent) is coupled out and fed to an evaluation unit for instance in the form of a laterally mounted array of photodiodes. In this case, each monitoring waveguide crosses between 0 and n−1 waveguides of the array, depending on the channel, on its way to a photodiode. The crossovers between the monitoring waveguides and the signal-carrying waveguides of the array lead to channel-dependent losses and to a crosstalk of the other waveguides of the array.
Generally, waveguide crossings have the disadvantage that they cause a signal loss, on the one hand, and bring about a crosstalk between the crossing waveguides, on the other hand. It is known in this case that the signal loss and the crosstalk decrease as the crossing angle increases. In order to keep down crosstalk and signal loss in a waveguide crossing, it is accordingly expedient to realize the largest possible crossing angles of greater than 40°. However, this disadvantageously leads to larger chip dimensions.
DE 100 64 579 A1 discloses a waveguide crossing in which one of the crossing waveguides is designed such that it is interrupted in the crossing region. This solution is suitable primarily for waveguide crossings in which the crossing waveguides are arranged essentially perpendicular to one another.